Patellar Injuries
Basics
Description
DislocationDescription
- Usually caused by twisting on a flexed knee
- Direct trauma is a less common cause
- Lateral dislocation of the patella is most common, with the patella displaced over the lateral femoral condyle
- Uncommon dislocations include superior, medial, and intra-articular dislocation
Fracture
- Direct trauma:
- Most common mechanism
- Direct blow or fall on patella, i.e., dashboard injury
- Usually results in comminuted or minimally displaced fracture, or open injury
- Indirect forces:
- Excessive tension through the extensor mechanism during deceleration from a fall, i.e., landing on feet from fall from moderate height (can also cause patellar tendon rupture)
- Avulsion injury from sudden contraction of the quadriceps tendon
- Usually results in transverse or displaced fracture (often both)
- Types of patellar fractures:
- Transverse: 50–80% (usually middle or lower third of patella)
- Comminuted (or stellate): 30–35%
- Longitudinal: 25%
- Osteochondral
Patellar Tendon Rupture
- Usually caused by forceful eccentric contraction of quadriceps muscle on a flexed knee during deceleration (e.g., jump landing and weight lifting)
- Often occurs in older athletes:
- Microtrauma from repetitive activity
Patellar Tendinitis
Overuse syndrome from repeated acceleration and deceleration (jumping, landing)
Etiology
DislocationEtiology
- Risk factors for patellar dislocation:
- Lower extremity malalignment (i.e., knock knee etc.)
- IT band tightness
- Generalized joint laxity
- Deficient vastus medialis
- Lateral insertion of patellar tendon
- Shallow patellar groove
- Patella alta (high-riding patella)
- Below the knee amputation
- Common injury in adolescent athletes, especially girls
- The younger the patient at the time of initial dislocation, the greater the risk of recurrence
Fracture
- Male:female ratio 2:1
- Highest incidence in those 20–50 yr old
Patellar Tendon Rupture
- Peak incidence in third and fourth decades:
- Often in athletes
- Risk factors:
- History of patellar tendinitis
- History of diabetes mellitus, previous steroid injections, rheumatoid arthritis, gout, systemic lupus erythematosus
- Previous major knee surgery
Patellar Tendinitis
- Microtears of tendon matrix from overuse
- Seen in high jumpers, volleyball and basketball players, runners
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Citation
Schaider, Jeffrey J., et al., editors. "Patellar Injuries." 5-Minute Emergency Consult, 6th ed., Lippincott Williams & Wilkins, 2020. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307210/all/Patellar_Injuries.
Patellar Injuries. In: Schaider JJJ, Barkin RMR, Hayden SRS, et al, eds. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307210/all/Patellar_Injuries. Accessed December 9, 2024.
Patellar Injuries. (2020). In Schaider, J. J., Barkin, R. M., Hayden, S. R., Wolfe, R. E., Barkin, A. Z., Shayne, P., & Rosen, P. (Eds.), 5-Minute Emergency Consult (6th ed.). Lippincott Williams & Wilkins. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307210/all/Patellar_Injuries
Patellar Injuries [Internet]. In: Schaider JJJ, Barkin RMR, Hayden SRS, Wolfe RER, Barkin AZA, Shayne PP, Rosen PP, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. [cited 2024 December 09]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307210/all/Patellar_Injuries.
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